The carbocationic polymerization of olefins is well-known and has been studied in detail. These processes can be initiated by systems producing carbocations. These initiating systems include Lewis and Bronsted acids, organic compounds such as halides in conjunction with Lewis acids, etc. (J. P. Kennedy: Cationic Polymerization of Olefins: A Critical Inventory. Wiley-Intersci). These processes produce high or low molecular weight polymers with various halide or olefinic functional groups, and can be further functionalized by post-polymerization reactions.
The living carbocationic polymerization of olefins such as isobutylene and styrene is a relatively new development. Prior art describes living carbocationic polymerizations producing polymers with controlled molecular weights and molecular weight distributions as low as M.sub.w /M.sub.n =1.05 (see U.S. Pat. No. 5,169,914). Suitable initiators include compounds with tertiary functional groups of the general formula shown below: ##STR2##
where R.sub.1, R.sub.2 and R.sub.3 can be hydrogen or aliphatic or aromatic alkyl groups, or aralkyl groups, and X can be a halogen, hydroxyl, ether or ester groups, or peroxides. These initiators, in conjunction with Lewis acids, Electron Pair Donors and Proton Traps, have successfully been used to produce homopolymers and random or block copolymers. The prior art has recently been reviewed in detail (Rubber Chem. Techn. 69,462 (1996). Multifunctional initiators carrying the above described tertiary functional groups have also been used to produce multiarm-star branched polymers (J. Polymer Sci., Chem. October 1997).
The above discussed living initiating systems produce halide-functionalized polymers, which can be further modified to yield other functional groups such as hydroxy- or ester. Unfortunately, these initiators are usually not available commercially and have to be synthesized by multistep synthetic routes.